This invention relates generally to the provision of refrigeration to a heat load wherein refrigeration is generated and provided to a heat load using a multicomponent refrigerant fluid.
Refrigeration is used extensively in the freezing of foods, production of pharmaceuticals, liquefaction of natural gas, and in many other applications wherein refrigeration is required to provide cooling duty to a heat load.
A recent significant advancement in the field of refrigeration is the development of refrigeration systems using multicomponent refrigerants which are able to generate refrigeration much more efficiently than conventional systems. These refrigeration systems, also known as mixed gas refrigerant systems or MGR systems, are particularly attractive for providing refrigeration at very low or cryogenic temperatures such as below xe2x88x9280xc2x0 F.
MGR systems, are typically more costly to install than are conventional vapor compression systems and are more complicated to operate. The high initial cost of an MGR system is particularly disadvantageous when an MGR system is designed to be much larger than nominally required by the specific application in order to be able to meet peak refrigeration requirements. Further costs are incurred to address reliability issues occasioned by the more complex nature of MGR systems.
Accordingly it is an object of this invention to provide a refrigeration system which will enable the use of an MGR system without the need to size the MGR system to meet peak refrigeration requirements of a heat load and without the need to add costly additional reliability systems to the basic MGR system.
The above and other objects, which will become apparent to those skilled in the art upon a reading of this disclosure, are attained by the present invention, one aspect of which is:
A method for providing refrigeration to a heat load comprising:
(A) compressing a multicomponent refrigerant fluid to provide compressed multicomponent refrigerant fluid, cooling the compressed multicomponent refrigerant fluid to provide cooled compressed multicomponent refrigerant fluid, and expanding the cooled compressed multicomponent refrigerant fluid to provide refrigeration bearing multicomponent refrigerant fluid;
(B) providing refrigeration from the refrigeration bearing multicomponent refrigerant fluid to a heat load and thereafter warming the multicomponent refrigerant fluid by indirect heat exchange with cooling compressed multicomponent refrigerant fluid; and
(C) passing cryogenic liquid to the heat load to provide cooling to the heat load.
Another aspect of the invention is:
Apparatus for providing refrigeration comprising:
(A) a heat load;
(B) at least one compressor, an autorefrigerator heat exchanger, an expansion device, and means for passing multicomponent refrigerant fluid from the compressor(s) to the autorefrigerator heat exchanger, from the autorefrigerator heat exchanger to the expansion device, from the expansion device to the heat load and from the heat load to the autorefrigerator heat exchanger; and
(C) a cryogenic liquid storage tank and means for passing cryogenic liquid from the cryogenic liquid storage tank to the heat load.
As used herein the term xe2x80x9cexpansionxe2x80x9d means to effect a reduction in pressure.
As used herein the term xe2x80x9cexpansion devicexe2x80x9d means apparatus for effecting expansion of a fluid.
As used herein the term xe2x80x9ccompressorxe2x80x9d means apparatus for effecting compression of a fluid.
As used herein the term xe2x80x9cmulticomponent refrigerant fluidxe2x80x9d means a fluid comprising two or more species and capable of generating refrigeration.
As used herein the term xe2x80x9crefrigerationxe2x80x9d means the capability to reject heat from a subambient temperature system.
As used herein the term xe2x80x9crefrigerant fluidxe2x80x9d means fluid in a refrigeration process which undergoes changes in temperature, pressure and possibly phase to absorb heat at a lower temperature and reject it at a higher temperature.
As used herein, the term xe2x80x9cvariable load refrigerantxe2x80x9d means a mixture of two or more components in proportions such that the liquid phase of those components undergoes a continuous and increasing temperature change between the bubble point and the dew point of the mixture. The bubble point of the mixture is the temperature, at a given pressure, wherein the mixture is all in the liquid phase but addition of heat will initiate formation of a vapor phase in equilibrium with the liquid phase. The dew point of the mixture is the temperature, at a given pressure, wherein the mixture is all in the vapor phase but extraction of heat will initiate formation of a liquid phase in equilibrium with the vapor phase. Hence, the temperature region between the bubble point and the dew point of the mixture is the region wherein both liquid and vapor phases coexist in equilibrium. In the preferred practice of this invention the temperature differences between the bubble point and the dew point for a variable load refrigerant generally is at least 10xc2x0 C., preferably at least 20xc2x0 C., and most preferably at least 50xc2x0 C.
As used herein the term xe2x80x9cheat loadxe2x80x9d means a stream or object that requires a reduction in energy, or removal of heat, to lower its temperature or to keep its temperature from rising.
As used herein the term xe2x80x9ccryogenic liquidxe2x80x9d means a liquid comprising at least one of liquid nitrogen, liquid carbon dioxide and liquid argon.